Sleep for longer when displaying still images

3 files changed, 26 insertions, 4 deletions

diff --git a/src/imv.c b/src/imv.c
index ff60d6e..5484c89 100644
--- a/src/imv.c
+++ b/src/imv.c
@@ -599,8 +599,18 @@ int imv_run(struct imv *imv)
       /* check stdin for any more paths */
       check_stdin_for_paths(imv);
     } else {
-      /* sleep a little bit so we don't waste CPU time */
-      SDL_Delay(10);
+      /* sleep until we have something to do */
+      unsigned int timeout = 1000; /* sleep up to a second */
+
+      /* if we need to display the next frame of an animation soon we should
+       * limit our sleep until the next frame is due */
+      const double next_frame_in = imv_loader_time_left(imv->loader);
+      if(next_frame_in > 0.0) {
+        timeout = (unsigned int)(next_frame_in * 1000.0);
+      }
+
+      /* go to sleep until an input event, etc. or the timeout expires */
+      SDL_WaitEventTimeout(NULL, timeout);
     }
   }
 
diff --git a/src/loader.c b/src/loader.c
index 4f8550c..cbebf2c 100644
--- a/src/loader.c
+++ b/src/loader.c
@@ -137,9 +137,11 @@ void imv_loader_time_passed(struct imv_loader *ldr, double dt)
   pthread_mutex_lock(&ldr->lock);
   if(ldr->num_frames > 1) {
     ldr->frame_time -= dt;
-    if(ldr->frame_time < 0) {
+    if(ldr->frame_time < 0.0) {
       get_frame = 1;
     }
+  } else {
+    ldr->frame_time = 0.0;
   }
   pthread_mutex_unlock(&ldr->lock);
 
@@ -148,6 +150,11 @@ void imv_loader_time_passed(struct imv_loader *ldr, double dt)
   }
 }
 
+double imv_loader_time_left(struct imv_loader *ldr)
+{
+  return ldr->frame_time;
+}
+
 static void *bg_new_img(void *data)
 {
   /* so we can poll for it */
@@ -187,7 +194,7 @@ static void *bg_new_img(void *data)
   FIMULTIBITMAP *mbmp = NULL;
   FIBITMAP *bmp = NULL;
   int width, height;
-  int raw_frame_time = 100; /* default to 100 */
+  int raw_frame_time = 0;
 
   if(fmt == FIF_GIF) {
     if(from_stdin) {
@@ -219,6 +226,8 @@ static void *bg_new_img(void *data)
     FreeImage_GetMetadata(FIMD_ANIMATION, frame, "FrameTime", &tag);
     if(FreeImage_GetTagValue(tag)) {
       raw_frame_time = *(int*)FreeImage_GetTagValue(tag);
+    } else {
+      raw_frame_time = 100; /* default value for gifs */
     }
     FreeImage_UnlockPage(mbmp, frame, 0);
 
diff --git a/src/loader.h b/src/loader.h
index ad01cb4..07fe068 100644
--- a/src/loader.h
+++ b/src/loader.h
@@ -69,6 +69,9 @@ void imv_loader_load_next_frame(struct imv_loader *ldr);
  * the loader will automatically load the next frame when it is due. */
 void imv_loader_time_passed(struct imv_loader *ldr, double dt);
 
+/* Ask the loader how long we can sleep for until the next frame */
+double imv_loader_time_left(struct imv_loader *ldr);
+
 #endif